Low cost attitude control system scanwheel development

In order to satisfy a growing demand for low cost attitude control systems for small spacecraft, development of low cost scanning horizon sensor coupled to a low cost/low power consumption Reaction Wheel Assembly was initiated. This report addresses the details of the versatile design resulting from this effort. Tradeoff analyses for each of the major components are included, as well as test data from an engineering prototype of the hardware

Infrared horizon sensor modeling for attitude determination and control: Analysis and mission experience

The work performed by the Attitude Determination and Control Section at the National Aeronautics and Space Administration/Goddard Space Flight Center in analyzing and evaluating the performance of infrared horizon sensors is presented. The results of studies performed during the 1960s are reviewed; several models for generating the Earth's infrared radiance profiles are presented; and the Horizon Radiance Modeling Utility, the software used to model the horizon sensor optics and electronics processing to computer radiance-dependent attitude errors, is briefly discussed. Also provided is mission experience from 12 spaceflight missions spanning the period from 1973 to 1984 and using a variety of horizon sensing hardware. Recommendations are presented for future directions for the infrared horizon sensing technology

Processing Pre-Existing Connect-The-Dots Puzzles For Educational Repurposing Applications

Connect-the-Dots puzzles are puzzles which contain labeled dots in a sequence. These puzzles are mostly designed as a way for children to hone in on their counting skills, while having fun. These same puzzles, which are available in abundance online and with modification, can be used to aid students in other areas of education such as spelling. Research shows that the addition of visual imagery provides a significant impact in spelling performance. The objective of this research is to develop an algorithm for processing Connect-the-Dots puzzles to assist in the replacement of the original numbers in the puzzle with characters that will help to facilitate an alternative educational purpose. In particular, the use of Optical Character Recognition (OCR) and image processing algorithms to process pre-existing Connect-the-Dots puzzles is explored. An algorithm was developed to locate and identify the numbers in the puzzles. The system is comprised of five components, namely, an Image Preprocessing component, a Dot Locator component, a Number Locator component, a Number Recognition component, and a Post-Processing component. To test the accuracy of the algorithm an experiment was conducted using 20 hand selected puzzles from an online source. The accuracy of the algorithm was evaluated, component by component, as well as overall, by visually capturing the make-up of the puzzles and comparing them to the results generated by the algorithm. Results show that the algorithm performed at an overall accuracy rate of 66%. However, the Dot Locator component performed at a rate of 100%, the Number Locator at a rate of 86%, and the Number Recognition at a rate of 76%. This research will aid in the development of an application that may provide educational benefits to children who are exposed to using technology for learning, at a young age

Processing Pre-Existing Connect-The-Dots Puzzles For Educational Repurposing Applications

Connect-the-Dots puzzles are puzzles which contain labeled dots in a sequence. These puzzles are mostly designed as a way for children to hone in on their counting skills, while having fun. These same puzzles, which are available in abundance online and with modification, can be used to aid students in other areas of education such as spelling. Research shows that the addition of visual imagery provides a significant impact in spelling performance. The objective of this research is to develop an algorithm for processing Connect-the-Dots puzzles to assist in the replacement of the original numbers in the puzzle with characters that will help to facilitate an alternative educational purpose. In particular, the use of Optical Character Recognition (OCR) and image processing algorithms to process pre-existing Connect-the-Dots puzzles is explored. An algorithm was developed to locate and identify the numbers in the puzzles. The system is comprised of five components, namely, an Image Preprocessing component, a Dot Locator component, a Number Locator component, a Number Recognition component, and a Post Processing component. To test the accuracy of the algorithm an experiment was conducted using 20 hand selected puzzles from an online source. The accuracy of the algorithm was evaluated, component by component, as well as overall, by visually capturing the make-up of the puzzles and comparing them to the results generated by the algorithm. Results show that the algorithm performed at an overall accuracy rate of 66%. However, the Dot Locator component performed at a rate of 100%, the Number Locator at a rate of 86%, and the Number Recognition at a rate of 76%. This research will aid in the development of an application that may provide educational benefits to children who are exposed to using technology for learning, at a young age

System and process for detecting and monitoring surface defects

A system and process for detecting and monitoring defects in large surfaces such as the field joints of the container segments of a space shuttle booster motor. Beams of semi-collimated light from three non-parallel fiber optic light panels are directed at a region of the surface at non-normal angles of expected incidence. A video camera gathers some portion of the light that is reflected at an angle other than the angle of expected reflectance, and generates signals which are analyzed to discern defects in the surface. The analysis may be performed by visual inspection of an image on a video monitor, or by inspection of filtered or otherwise processed images. In one alternative embodiment, successive predetermined regions of the surface are aligned with the light source before illumination, thereby permitting efficient detection of defects in a large surface. Such alignment is performed by using a line scan gauge to sense the light which passes through an aperture in the surface. In another embodiment a digital map of the surface is created, thereby permitting the maintenance of records detailing changes in the location or size of defects as the container segment is refurbished and re-used. The defect detection apparatus may also be advantageously mounted on a fixture which engages the edge of a container segment

Continuous prediction of Spartan visibility from Orbiter over modeled free-flight mission

Orbital operations in the neighborhood of other satellites or free-flying objects need the ability to see and detect such objects optically. This ability depends primarily on the brightness of the object relative to other sources present. The present analysis and computational procedure provides a means for predicting the visual brightness of a satellite when viewed from a nearby satellite in the same orbit. It is designed specifically for estimating the brightness of Spartan free-flyers from the STS Orbiters which release and later retrieve them, but the basic methods are applicable to other satellite-to-satellite visibility prediction problems. The Spartan reflector model defined herein is illuminated both by direct solar radiation and by the earth (albedo), producing a model source of defined directional intensity. The intensity in the Orbiter direction (along orbit) yields the desired maximum range directly. The required geometric and photometric calculations involve a number of angles in space, which are readily computed from the basic directions defining their sides. The time-dependent directions are determined by straightforward calculation from fundamental relationships and constants

METHOD OF PROTECTING SPECIALLY IMPORTANT OBJECTS BASED ON THE APPLICATION OF THE BISTATIC RADIOLOCATION TECHNIQUE

The solution of the tasks assigned to the National Guard of the state implies the presence of certain forces and means with the appropriate technical equipment. A well-known place among such tasks is security of important state facilities. Various physical effects and methods, including radar, are used to create security systems. The development of radar technology and technology made it possible to increase both the quantity and quality of the received information, as well as the use of radar stations for observing living objects. The industry today produces bioradioradars for detecting people and controlling their movements. All samples are made in a single-position version and have a relatively high cost, the fact of their work is easily detected, which facilitates their suppression, including force. In order to increase the secrecy of work, it is proposed to use the methods of separated, more precisely, bistatic location to control the area in front of particularly important objects. The defining detection index is the effective reflective surface (ERS), which is about 1 m2 for a person. Equipment, weapons and protective equipment contributes to the increase in the ERS. Given the small reflective surface of biological objects, it is proposed to limit the area of responsibility to the sector form in which, at a certain bistatic angle, the effect of a significant increase in the signal/(interference+noise) ratio is manifested. For a specific definition of the gain, it is necessary to choose the operating frequency of the bistatic system and its geometry. For greater secrecy, it is advisable to use the transmitters of radio and television broadcasting, mobile communications, etc. The estimates found, for example, when using digital television transmitters (T2), indicate that the creation of a secretive bistatic system is quite possible – at least in a geometric interpretation

Contrasting behaviour from two Be/X-ray binary pulsars: insights into differing neutron star accretion modes

In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4s and 85.4s pulsations were considered to originate from new Be/X-ray binary (BeXRB) pulsars with unknown locations. Using rapid follow-up INTEGRAL and XMM-Newton observations, we show the first pulsar (designated SXP175) to be coincident with a candidate high-mass X-ray binary (HMXB) in the northern bar region of the SMC undergoing a small Type II outburst. The orbital period (87d) and spectral class (B0-B0.5IIIe) of this system are determined and presented here for the first time. The second pulsar is shown not to be new at all, but is consistent with being SXP91.1 - a pulsar discovered at the very beginning of the 13 year long RXTE key monitoring programme of the SMC. Whilst it is theoretically possible for accreting neutron stars to change spin period so dramatically over such a short time, the X-ray and optical data available for this source suggest this spin-up is continuous during long phases of X-ray quiescence, where accretion driven spin-up of the neutron star should be minimal.Comment: 13 pages, 16 figures, accepted for publication in MNRA

Chromatic dependence of first-order optical properties of the eye

Abstract: Many first-order optical properties depend on chromatic dispersion and, hence, on frequency of light. The purpose of this theoretical study is to investigate the dependence of first-order optical properties of model eyes on frequency. In this study we are purposefully not concerned with subjective measurements. Instead, definitions are obtained that are general for optical systems that have astigmatic and decentred elements, and then simplified for Gaussian systems. In linear optics the transference is a matrix that is a complete representation of the effects of the system on a ray traversing it. Almost all of the familiar optical properties of the system can be obtained from the transference. From the transference S we obtain the four fundamental properties namely dilation A, disjugacy B, divergence C and divarication D, submatrices of S. Transferences are symplectic and do not define a linear space. Linear spaces are amenable to statistical analyses and therefore a number of mappings to linear spaces are investigated, including the Cayley and logarithmic mappings to Hamiltonian space and the four characteristic matrices. In each case, the individual entries of the transform are studied for their dependence on frequency and then the chromatic dependence relationship between the entries is compared graphically.M.Phil. (Optometry